REVIEWED: Avoid program crash if GPU data is tried to be loaded before `InitWindow()` #4751

Following raylib design, a warning log message is shown and program can continue execution.
Some early return checks have been added on most  critical functions.
[rtext] Previous implementation checking `isGpuReady` cross-module variable is not needed any more, resulting in a more decoupled code, load failure is managed at rlgl level

src/platforms/rcore_android.c

@@ -84,7 +84,6 @@ typedef struct {
 // Global Variables Definition
 //----------------------------------------------------------------------------------
 extern CoreData CORE;                   // Global CORE state context
-extern bool isGpuReady;                 // Flag to note GPU has been initialized successfully
 static PlatformData platform = { 0 };   // Platform specific data
 
 //----------------------------------------------------------------------------------
@@ -1042,7 +1041,6 @@ static void AndroidCommandCallback(struct android_app *app, int32_t cmd)
                     // Initialize OpenGL context (states and resources)
                     // NOTE: CORE.Window.currentFbo.width and CORE.Window.currentFbo.height not used, just stored as globals in rlgl
                     rlglInit(CORE.Window.currentFbo.width, CORE.Window.currentFbo.height);
-                    isGpuReady = true;
 
                     // Setup default viewport
                     // NOTE: It updated CORE.Window.render.width and CORE.Window.render.height

src/rcore.c

@@ -387,11 +387,6 @@ RLAPI const char *raylib_version = RAYLIB_VERSION;  // raylib version exported s
 
 CoreData CORE = { 0 };                      // Global CORE state context
 
-// Flag to note GPU acceleration is available,
-// referenced from other modules to support GPU data loading
-// NOTE: Useful to allow Texture, RenderTexture, Font.texture, Mesh.vaoId/vboId, Shader loading
-bool isGpuReady = false;
-
 #if defined(SUPPORT_SCREEN_CAPTURE)
 static int screenshotCounter = 0;           // Screenshots counter
 #endif
@@ -697,7 +692,6 @@ void InitWindow(int width, int height, const char *title)
     // Initialize rlgl default data (buffers and shaders)
     // NOTE: Current fbo size stored as globals in rlgl for convenience
     rlglInit(CORE.Window.currentFbo.width, CORE.Window.currentFbo.height);
-    isGpuReady = true; // Flag to note GPU has been initialized successfully
 
     // Setup default viewport
     SetupViewport(CORE.Window.currentFbo.width, CORE.Window.currentFbo.height);
@@ -1266,7 +1260,14 @@ Shader LoadShaderFromMemory(const char *vsCode, const char *fsCode)
 
     shader.id = rlLoadShaderCode(vsCode, fsCode);
 
-    if (shader.id == rlGetShaderIdDefault()) shader.locs = rlGetShaderLocsDefault();
+    if (shader.id == 0)
+    {
+        // Shader could not be loaded but we still load the location points to avoid potential crashes
+        // NOTE: All locations set to -1 (no location)
+        shader.locs = (int *)RL_CALLOC(RL_MAX_SHADER_LOCATIONS, sizeof(int));
+        for (int i = 0; i < RL_MAX_SHADER_LOCATIONS; i++) shader.locs[i] = -1;
+    }
+    else if (shader.id == rlGetShaderIdDefault()) shader.locs = rlGetShaderLocsDefault();
     else if (shader.id > 0)
     {
         // After custom shader loading, we TRY to set default location names
@@ -1282,9 +1283,9 @@ Shader LoadShaderFromMemory(const char *vsCode, const char *fsCode)
 
         // NOTE: If any location is not found, loc point becomes -1
 
+        // Load shader locations array
+        // NOTE: All locations set to -1 (no location)
         shader.locs = (int *)RL_CALLOC(RL_MAX_SHADER_LOCATIONS, sizeof(int));
-
-        // All locations reset to -1 (no location)
         for (int i = 0; i < RL_MAX_SHADER_LOCATIONS; i++) shader.locs[i] = -1;
 
         // Get handles to GLSL input attribute locations

src/rlgl.h

@@ -1153,6 +1153,7 @@ static double rlCullDistanceFar = RL_CULL_DISTANCE_FAR;
 #if defined(GRAPHICS_API_OPENGL_33) || defined(GRAPHICS_API_OPENGL_ES2)
 static rlglData RLGL = { 0 };
 #endif  // GRAPHICS_API_OPENGL_33 || GRAPHICS_API_OPENGL_ES2
+static bool isGpuReady = false;
 
 #if defined(GRAPHICS_API_OPENGL_ES2) && !defined(GRAPHICS_API_OPENGL_ES3)
 // NOTE: VAO functionality is exposed through extensions (OES)
@@ -2283,6 +2284,8 @@ static void GLAPIENTRY rlDebugMessageCallback(GLenum source, GLenum type, GLuint
 // Initialize rlgl: OpenGL extensions, default buffers/shaders/textures, OpenGL states
 void rlglInit(int width, int height)
 {
+    isGpuReady = true;
+
     // Enable OpenGL debug context if required
 #if defined(RLGL_ENABLE_OPENGL_DEBUG_CONTEXT) && defined(GRAPHICS_API_OPENGL_43)
     if ((glDebugMessageCallback != NULL) && (glDebugMessageControl != NULL))
@@ -2395,6 +2398,7 @@ void rlglClose(void)
 #if defined(GRAPHICS_API_OPENGL_11_SOFTWARE)
     swClose(); // Unload sofware renderer resources
 #endif
+    isGpuReady = false;
 }
 
 // Load OpenGL extensions
@@ -2799,6 +2803,7 @@ int *rlGetShaderLocsDefault(void)
 rlRenderBatch rlLoadRenderBatch(int numBuffers, int bufferElements)
 {
     rlRenderBatch batch = { 0 };
+    if (!isGpuReady) { TRACELOG(RL_LOG_WARNING, "GL: GPU is not ready to load data, trying to load before InitWindow()?"); return batch; }
 
 #if defined(GRAPHICS_API_OPENGL_33) || defined(GRAPHICS_API_OPENGL_ES2)
     // Initialize CPU (RAM) vertex buffers (position, texcoord, color data and indexes)
@@ -3253,6 +3258,7 @@ bool rlCheckRenderBatchLimit(int vCount)
 unsigned int rlLoadTexture(const void *data, int width, int height, int format, int mipmapCount)
 {
     unsigned int id = 0;
+    if (!isGpuReady) { TRACELOG(RL_LOG_WARNING, "GL: GPU is not ready to load data, trying to load before InitWindow()?"); return id; }
 
     glBindTexture(GL_TEXTURE_2D, 0);    // Free any old binding
 
@@ -3411,6 +3417,7 @@ unsigned int rlLoadTexture(const void *data, int width, int height, int format,
 unsigned int rlLoadTextureDepth(int width, int height, bool useRenderBuffer)
 {
     unsigned int id = 0;
+    if (!isGpuReady) { TRACELOG(RL_LOG_WARNING, "GL: GPU is not ready to load data, trying to load before InitWindow()?"); return id; }
 
 #if defined(GRAPHICS_API_OPENGL_33) || defined(GRAPHICS_API_OPENGL_ES2)
     // In case depth textures not supported, we force renderbuffer usage
@@ -3469,6 +3476,7 @@ unsigned int rlLoadTextureDepth(int width, int height, bool useRenderBuffer)
 unsigned int rlLoadTextureCubemap(const void *data, int size, int format, int mipmapCount)
 {
     unsigned int id = 0;
+    if (!isGpuReady) { TRACELOG(RL_LOG_WARNING, "GL: GPU is not ready to load data, trying to load before InitWindow()?"); return id; }
 
 #if defined(GRAPHICS_API_OPENGL_33) || defined(GRAPHICS_API_OPENGL_ES2)
     int mipSize = size;
@@ -3813,6 +3821,7 @@ unsigned char *rlReadScreenPixels(int width, int height)
 unsigned int rlLoadFramebuffer(void)
 {
     unsigned int fboId = 0;
+    if (!isGpuReady) { TRACELOG(RL_LOG_WARNING, "GL: GPU is not ready to load data, trying to load before InitWindow()?"); return fboId; }
 
 #if (defined(GRAPHICS_API_OPENGL_33) || defined(GRAPHICS_API_OPENGL_ES2)) && defined(RLGL_RENDER_TEXTURES_HINT)
     glGenFramebuffers(1, &fboId);       // Create the framebuffer object
@@ -3928,6 +3937,7 @@ void rlUnloadFramebuffer(unsigned int id)
 unsigned int rlLoadVertexBuffer(const void *buffer, int size, bool dynamic)
 {
     unsigned int id = 0;
+    if (!isGpuReady) { TRACELOG(RL_LOG_WARNING, "GL: GPU is not ready to load data, trying to load before InitWindow()?"); return id; }
 
 #if defined(GRAPHICS_API_OPENGL_33) || defined(GRAPHICS_API_OPENGL_ES2)
     glGenBuffers(1, &id);
@@ -3942,6 +3952,7 @@ unsigned int rlLoadVertexBuffer(const void *buffer, int size, bool dynamic)
 unsigned int rlLoadVertexBufferElement(const void *buffer, int size, bool dynamic)
 {
     unsigned int id = 0;
+    if (!isGpuReady) { TRACELOG(RL_LOG_WARNING, "GL: GPU is not ready to load data, trying to load before InitWindow()?"); return id; }
 
 #if defined(GRAPHICS_API_OPENGL_33) || defined(GRAPHICS_API_OPENGL_ES2)
     glGenBuffers(1, &id);
@@ -4107,12 +4118,12 @@ void rlDisableStatePointer(int vertexAttribType)
 unsigned int rlLoadVertexArray(void)
 {
     unsigned int vaoId = 0;
+    if (!isGpuReady) { TRACELOG(RL_LOG_WARNING, "GL: GPU is not ready to load data, trying to load before InitWindow()?"); return vaoId; }
+
 #if defined(GRAPHICS_API_OPENGL_33) || defined(GRAPHICS_API_OPENGL_ES2)
-    if (RLGL.ExtSupported.vao)
-    {
-        glGenVertexArrays(1, &vaoId);
-    }
+    if (RLGL.ExtSupported.vao) glGenVertexArrays(1, &vaoId);
 #endif
+
     return vaoId;
 }
 
@@ -4167,6 +4178,7 @@ void rlUnloadVertexBuffer(unsigned int vboId)
 unsigned int rlLoadShaderCode(const char *vsCode, const char *fsCode)
 {
     unsigned int id = 0;
+    if (!isGpuReady) { TRACELOG(RL_LOG_WARNING, "GL: GPU is not ready to load data, trying to load before InitWindow()?"); return id; }
 
 #if defined(GRAPHICS_API_OPENGL_33) || defined(GRAPHICS_API_OPENGL_ES2)
     unsigned int vertexShaderId = 0;
@@ -4309,6 +4321,7 @@ unsigned int rlCompileShader(const char *shaderCode, int type)
 unsigned int rlLoadShaderProgram(unsigned int vShaderId, unsigned int fShaderId)
 {
     unsigned int programId = 0;
+    if (!isGpuReady) { TRACELOG(RL_LOG_WARNING, "GL: GPU is not ready to load data, trying to load before InitWindow()?"); return programId; }
 
 #if defined(GRAPHICS_API_OPENGL_33) || defined(GRAPHICS_API_OPENGL_ES2)
     GLint success = 0;

src/rmodels.c

@@ -1282,6 +1282,8 @@ void UploadMesh(Mesh *mesh, bool dynamic)
 
 #if defined(GRAPHICS_API_OPENGL_33) || defined(GRAPHICS_API_OPENGL_ES2)
     mesh->vaoId = rlLoadVertexArray();
+    if (mesh->vaoId == 0) return;
+
     rlEnableVertexArray(mesh->vaoId);
 
     // NOTE: Vertex attributes must be uploaded considering default locations points and available vertex data
@@ -1470,6 +1472,8 @@ void DrawMesh(Mesh mesh, Material material, Matrix transform)
     // Bind shader program
     rlEnableShader(material.shader.id);
 
+    if (material.shader.locs == NULL) return;
+
     // Send required data to shader (matrices, values)
     //-----------------------------------------------------
     // Upload to shader material.colDiffuse

src/rtext.c

@@ -127,13 +127,12 @@
 //----------------------------------------------------------------------------------
 // Global variables
 //----------------------------------------------------------------------------------
-extern bool isGpuReady;
 #if defined(SUPPORT_DEFAULT_FONT)
 // Default font provided by raylib
 // NOTE: Default font is loaded on InitWindow() and disposed on CloseWindow() [module: core]
 static Font defaultFont = { 0 };
 #endif
-static int textLineSpacing = 2;                 // Text vertical line spacing in pixels (between lines)
+static int textLineSpacing = 2; // Text vertical line spacing in pixels (between lines)
 
 //----------------------------------------------------------------------------------
 // Other Modules Functions Declaration (required by text)
@@ -164,8 +163,8 @@ extern void LoadFontDefault(void)
 {
     #define BIT_CHECK(a,b) ((a) & (1u << (b)))
 
-    // Check to see if we have allready allocated the font for an image, and if we don't need to upload, then just return
-    if ((defaultFont.glyphs != NULL) && !isGpuReady) return;
+    // Check to see if we have already allocated the font for an image, and if we don't need to upload, then just return
+    if (defaultFont.glyphs != NULL) return;
 
     // NOTE: Using UTF-8 encoding table for Unicode U+0000..U+00FF Basic Latin + Latin-1 Supplement
     // Ref: http://www.utf8-chartable.de/unicode-utf8-table.pl
@@ -263,17 +262,14 @@ extern void LoadFontDefault(void)
         counter++;
     }
 
-    if (isGpuReady)
-    {
-        defaultFont.texture = LoadTextureFromImage(imFont);
+    defaultFont.texture = LoadTextureFromImage(imFont);
 
-        // we have already loaded the font glyph data an image, and the GPU is ready, we are done
-        // if we don't do this, we will leak memory by reallocating the glyphs and rects
-        if (defaultFont.glyphs != NULL)
-        {
-            UnloadImage(imFont);
-            return;
-        }
+    // we have already loaded the font glyph data an image, and the GPU is ready, we are done
+    // if we don't do this, we will leak memory by reallocating the glyphs and rects
+    if (defaultFont.glyphs != NULL)
+    {
+        UnloadImage(imFont);
+        return;
     }
 
     // Reconstruct charSet using charsWidth[], charsHeight, charsDivisor, glyphCount
@@ -330,7 +326,7 @@ extern void LoadFontDefault(void)
 extern void UnloadFontDefault(void)
 {
     for (int i = 0; i < defaultFont.glyphCount; i++) UnloadImage(defaultFont.glyphs[i].image);
-    if (isGpuReady) UnloadTexture(defaultFont.texture);
+    UnloadTexture(defaultFont.texture);
     RL_FREE(defaultFont.glyphs);
     RL_FREE(defaultFont.recs);
     defaultFont.glyphCount = 0;
@@ -384,17 +380,15 @@ Font LoadFont(const char *fileName)
     {
         Image image = LoadImage(fileName);
         if (image.data != NULL) font = LoadFontFromImage(image, MAGENTA, FONT_TTF_DEFAULT_FIRST_CHAR);
+        else font = GetFontDefault();
         UnloadImage(image);
     }
 
-    if (isGpuReady)
+    if (font.texture.id == 0) TRACELOG(LOG_WARNING, "FONT: [%s] Failed to load font texture -> Using default font", fileName);
+    else
     {
-        if (font.texture.id == 0) TRACELOG(LOG_WARNING, "FONT: [%s] Failed to load font texture -> Using default font", fileName);
-        else
-        {
-            SetTextureFilter(font.texture, TEXTURE_FILTER_POINT);    // By default, we set point filter (the best performance)
-            TRACELOG(LOG_INFO, "FONT: Data loaded successfully (%i pixel size | %i glyphs)", font.baseSize, font.glyphCount);
-        }
+        SetTextureFilter(font.texture, TEXTURE_FILTER_POINT); // By default, we set point filter (the best performance)
+        TRACELOG(LOG_INFO, "FONT: Data loaded successfully (%i pixel size | %i glyphs)", font.baseSize, font.glyphCount);
     }
 
     return font;
@@ -515,7 +509,7 @@ Font LoadFontFromImage(Image image, Color key, int firstChar)
     };
 
     // Set font with all data parsed from image
-    if (isGpuReady) font.texture = LoadTextureFromImage(fontClear); // Convert processed image to OpenGL texture
+    font.texture = LoadTextureFromImage(fontClear); // Convert processed image to OpenGL texture
     font.glyphCount = index;
     font.glyphPadding = 0;
 
@@ -584,7 +578,7 @@ Font LoadFontFromMemory(const char *fileType, const unsigned char *fileData, int
         font.glyphPadding = FONT_TTF_DEFAULT_CHARS_PADDING;
 
         Image atlas = GenImageFontAtlas(font.glyphs, &font.recs, font.glyphCount, font.baseSize, font.glyphPadding, 0);
-        if (isGpuReady) font.texture = LoadTextureFromImage(atlas);
+        font.texture = LoadTextureFromImage(atlas);
 
         // Update glyphs[i].image to use alpha, required to be used on ImageDrawText()
         for (int i = 0; i < font.glyphCount; i++)
@@ -1008,7 +1002,7 @@ void UnloadFont(Font font)
     if (font.texture.id != GetFontDefault().texture.id)
     {
         UnloadFontData(font.glyphs, font.glyphCount);
-        if (isGpuReady) UnloadTexture(font.texture);
+        UnloadTexture(font.texture);
         RL_FREE(font.recs);
 
         TRACELOGD("FONT: Unloaded font data from RAM and VRAM");
@@ -1339,8 +1333,7 @@ Vector2 MeasureTextEx(Font font, const char *text, float fontSize, float spacing
 {
     Vector2 textSize = { 0 };
 
-    if ((isGpuReady && (font.texture.id == 0)) ||
-        (text == NULL) || (text[0] == '\0')) return textSize; // Security check
+    if ((font.texture.id == 0) || (text == NULL) || (text[0] == '\0')) return textSize; // Security check
 
     int size = TextLength(text);    // Get size in bytes of text
     int tempByteCounter = 0;        // Used to count longer text line num chars
@@ -2481,7 +2474,7 @@ static Font LoadBMFont(const char *fileName)
 
     RL_FREE(imFonts);
 
-    if (isGpuReady) font.texture = LoadTextureFromImage(fullFont);
+    font.texture = LoadTextureFromImage(fullFont);
 
     // Fill font characters info data
     font.baseSize = fontSize;
@@ -2523,7 +2516,7 @@ static Font LoadBMFont(const char *fileName)
     UnloadImage(fullFont);
     UnloadFileText(fileText);
 
-    if (isGpuReady && (font.texture.id == 0))
+    if (font.texture.id == 0)
     {
         UnloadFont(font);
         font = GetFontDefault();